diff --git a/runtime/pb/wire.lua b/runtime/pb/wire.lua
index 8e21add2974bcf573c114e2a3e54985a02ab8890..0b6046da420859ef5c600248b20adde1a77ef285 100644
--- a/runtime/pb/wire.lua
+++ b/runtime/pb/wire.lua
@@ -50,6 +50,11 @@ -- Fast path: small non-negative Lua numbers (0..127) become a single
 -- string.char(n) call with no cdata allocation, no `out` table, no
 -- table.concat. Covers most length prefixes for short strings, many
 -- enum ordinals, and most small int values in typical RPC payloads.
+--
+-- We deliberately do NOT extend the fast path to 2-4 byte values:
+-- growing the function past the LuaJIT inline budget makes parent
+-- traces stop inlining it, which costs more (~30% bench regression
+-- on 1-byte-dominant workloads) than the rare multi-byte case gains.
 local function encode_varint(n)
     if type(n) == 'number' and n >= 0 and n < 0x80 then
         return string.char(n)